package com.huawei.mapreduce.wordcount;

import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class WordCountApp {
    public static class MyMapper extends Mapper<LongWritable, Text, Text, LongWritable>{
        @Override
        protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, LongWritable>.Context context) throws IOException, InterruptedException {
            String line = value.toString();
            String[] splited = line.split("\t");
            for (String word : splited) {
                Text k2 = new Text(word);
                LongWritable v2 = new LongWritable(1);
                context.write(k2, v2);
            }
        }
    }

    public static class MyReducer extends Reducer<Text, LongWritable, Text, LongWritable>{
        @Override
        protected void reduce(Text k2, Iterable<LongWritable> v2s,
                              Reducer<Text, LongWritable, Text, LongWritable>.Context context) throws IOException, InterruptedException {
            long count = 0L;
            for (LongWritable times : v2s) {
                count += times.get();
            }
            LongWritable v3 = new LongWritable(count);
            context.write(k2, v3);
        }
    }

    public static void main(String[] args) throws Exception{
        Configuration conf = new Configuration();
        Job job = Job.getInstance(conf , WordCountApp.class.getSimpleName());
        //必须指定
        job.setJarByClass(WordCountApp.class);

        //指定本业务job要使用的Mapper业务类
        job.setMapperClass(MyMapper.class);
        //指定mapper输出数据的<k2,v2>的类型
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(LongWritable.class);

        //指定本业务job要使用的Reducer业务类
        job.setReducerClass(MyReducer.class);
        //指定reducer输出数据的<k3,v3>的类型
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(LongWritable.class);

        //输入数据来自哪里
        FileInputFormat.setInputPaths(job, new Path(args[0]));
        //输出数据写到哪里
        FileOutputFormat.setOutputPath(job, new Path(args[1]));

        //true表示将运行进度等信息及时输出给用户
        boolean res = job.waitForCompletion(true);
        System.exit(res?0:1);
    }
}